Switching mechanisms



y 1963 G. J. LYNCH ETAL 3,098,129

SWITCHING MECHANISMS Filed Sept. 25. 1958 INVENTOR GEORGE J. LY CH WILLIAM J. ORMSTON ATTORNEYS United States Patent 3,098,129 SWITCHING MECHANISMS George J. Lynch, Bloomfield, and William J. Ormston, Nutley, N.J., assignors to Mycalex Electronics Corporation, Clifton, N.J., a corporation of New York Filed Sept. 23, 1958, Ser. No. 762,7l2 4 Claims. (Cl. 200-11) This invention relates to switching mechanisms and particularly to high speed switching mechanisms for use in telemetering systems in which a large number of continuous switching operations must be carried out.

In telemetering systems, it is a common expedient to employ a high speed switching mechanism as a multiplixing switch for sequentially closing circuits from data supplying devices to a transmitting means so that the data will be sequentially supplied to receiving apparatus remote from the source of the data. Such an expedient is commonly used in airborne telemetcring systems such as systems for meter-ing the performance of rockets, missiles and aircraft. In such systems reliability and minimization of weight and bulk are of paramount importance.

In standard commutation switches there is provided at least one circular ring of spaced contacts and a continuous slip ring. At least some of the contacts are connnected to the data supplying devices referred to above. A rotating brush assembly is adapted to engage the contacts in the row of contacts and further to engage the slip ring whereby to sequentially close the circuits between said contacts and said slip ring in order to supply in sequence the data from the data supplying devices to a suitable transmitting means.

There are two common arrangements for connecting the data supplying devices to the commutation switch contacts. In one of the arrangements each of the contacts is connected to a data supplying device. In such an arrangement, assuming the brush to be larger than the spacing between contacts, it will be obvious that as a brush moves from one contact to the next contact, it will engage the next contact before it disengages from said one contact whereby to give a make-before-break system. That is, if one circuit is closed, the next adjacent circuit will become closed as the brush progresses around the ring of contacts before said one circuit is open.

Another common ararngement is to have data supplying devices connected to alternate contacts with the contacts in between being completely de-enengized. Assuming the brush engaging the contacts is not of sufficient longitudinal extent to bridge two contacts then clearly one circuit will be open before the next circuit will be closed as the brush moves around the ring of contacts. Such an arrangement is commonly known as a break-before-make arrangement.

Different telemetering systems require dilferent periods of time during which a signal is supplied to transmitting means. The period during which a signal is supplied is generally known as the on-time and the period during which no signal is supplied is commonly known as the off-time. Assuming a circular row of contacts which are all spaced equidistant from one another and with alternate contacts energized the on-time is equal to the percentage of time that a circuit is closed as a brush moves from one position on an energized contact to a corresponding position on the next energized contact. The ontime can be stated quantitatively by the following expres- SlOIl.

on-time length of energized contact +length of brush Analyzing the above equation it will be seen that the ice on-time can be varied by varying either the length of the contacts, the spacing between adjacent contacts or the length of the brush. The possibilities of varying the length of the contacts are limited by practical production considerations. First of all, it is often desirable to have a large number of relatively short contacts in one row so as to minimize the amount of space taken up by the commutation switch. Accordingly, there is a constant pressure for making a commutator plate with smaller and smaller contacts, thereby greatly restricting the possibility of varying the length of the contacts. Moreover, it is possible to vary the on-time by having the energized contacts of a different dimension than the de-energized contacts. This can and has been done in the past. However, there is a wide variety of on-times required for the wide variety of telemetering systems employing switches of the type described herein. Thereforc, if the commutator plate is to be a molded article, which is preferred, there will have to be a wide variety of costly tools, thereby rendering the cost of each plate almost prohibitive. The spacing between contacts can also theoretically be varied to vary on-tirne but this is also greatly restricted. First of all, there is a minimum spacing between contacts for any given commutator plate since the insulation resistance between adjacent contacts must be above a predetermined value. As for increasing the spacing between contacts above the minimum this will cause the circular row to have a relatively large diameter and thereby be wasteful of space. Accordingly, the opportunities for varying on-time by varying contact spacing are extremely limited.

The remaining means for varying the on-time is by varying the brush length. However, in United States patent application Serial No. 649,150, now Patent No. 2,975,246, filed by George I. Lynch and George Golik, on March 28, 1957, for Switching Mechanisms, which application is assigned to the assignee hereof, it is disclosed that for optimum commutation the length of the brush which moves over the contacts is limited to a definite relationship to the spacing between contacts. Particularly, the longitudinal extent of the brush, that is the length of the brush, should be between 1.4 and 2.5 times the contact spacing and preferably 1.85 times the contact spacing. With brushes of such proportion a superior signal is achieved particularly in metal-to-metal brush and contact assemblies due to the inherent ability of such brushes to clean themselves and to maintain good surface-to-surf-ace engagement with the contacts. Accordingly, there is very limited possibility for varying the on-time by changing the length of a single brush and if the length of the brush is substantially changed from the optimum, the quality of the signals commutated by the switch is not good enough for the reliability sought. When a single brush made in accordance with the preferred proportioning of Lynch and Golik is employed to engage a series of identical contacts in a break-before-make system, it has been found that the on-time is about 60%.

There is further described in said aforementioned Lynch and Golik application a brush assembly wherein two electrically connected brushes are aligned with respect to their path of movement and are spaced from one another along said path. With such a multiple brush arrangement in a break-before-make system and with the same relationship between the brush lengths and the contact spacing, it has been found that an on-time of about 99% or more can be achieved. However, on-times between about 60% and about 99% are not achievable with the commutator plate configuration described.

. The main object of the present invention is to provide a new and improved switching mechanism having provision for a continuous adjustment of the on-time.

Another object of the present invention is the provision of a new and improved commutation switch having a ring of substantially identical contacts and provision for varying the on-time over a continuous range.

A further object of the present invention is the provision of a new and improved brush assembly for a commutation switch having provision for a continuous adjustment of the on-time for a switch associated with said brush assembly.

A still further object of the present invention is the provision of a new and improved commutation switch having a plurality of contacts arranged in a circular row, which contacts have linear leading and trailing edges, and a brush assembly adapted to cooperate with said ring of contacts, the brush assembly having provision for continuous adjustment of the on-time.

The above and other objects, characteristics and features of the present invention will be more fully understood from the following description taken in connection with the accompanying illustrative drawing.

In the drawing:

FIG. 1 is a vertical view partly in section and partly in elevation of a switching mechanism embodying the present invention;

FIG. 2 is a sectional view taken along the line 22 of FIG. 1;

FIG. 3 is a plan view of the brush assembly with some parts deleted to more adequately illustrate other parts of the invention;

FIG. 4 is a diagrammatic fragmentary side elevational view illustrating the engagement of the brushes with the contacts;

, FIG. 5 is a view similar to FIG. 4 showing another condition; and

FIG. 6 is a view similar to FIGS. another condition.

Referring now to the drawing in detail, a commutation switch embodying the present invention is generally designated by the reference numeral 10. Switch 10 includes a cylindrical support member 12 having integrally formed thereon an end piece 14, the other end 16 being open. End piece 14 is provided with a central aperture 18 and two oppositely disposed apertures 20 and 22 for reasons which will appear hereinafter. Secured to the end piece 14 by suitable securing elements such as screws 28 is a motor means 24 which may be a simple electric motor or a motor together with a gear train, as may be desired. Motor 24 includes output shaft 26 which extends through aperture 18 in end piece 14 with clearance.

Overlying the open end 16 of cylindrical member 12 is a commutator plate 30. Commutator plate 30 is here shown as being of substantially the same peripheral extent as cylindrical member 12 and lies in abutting relation therewith. To secure plate 30 to member 12 a plurality of securing elements such as screws 32 are employed. Commutator plate 30 is preferably 'a molded article having a ring of closely spaced contacts 34 adjacent the periphery thereof and "a continuous slip ring disposed inwardly of said circular row of contacts 34 and concentric therewith. The circular row of contacts 34 and the slip ring 36 are all held in fixed relation by a suitable electrical insulating material 37. Preferably the insulating material in commutator plate 30 is a vitreo-micaceous material such as glass-bonded mica or a ceramoplastic and plate 30 is most preferably manufactured by injection molding techniques. By employing an injection molded commutator plate of vitreo-micacecus material the plate 30 will have excellent dimensional stability, resistance to deterioration under high temperature conditions and the contacts 34 in the slip ring 36 will be rigidly held against displacement in use. To assure against the displacement of the contacts and slip ring they are preferablyall provided with re-entrant portions 38 to mechanically lock them relative to the vitreo-micaceous insulatprovided with a terminal 40 disposed opposite the rear ing material. As shown herein each of the contacts 34 is surface 42 of plate 30 and the slip ring is provided with 4 and 5 showing still 4 one or more terminals 44 extending beyond the rear surface '42 of plate 30. The front surface 46 of the contacts 34 are all flush relative to one another and are preferably flush with the front surface 48 of the slip ring 36.

Although a wide variety of materials may be employed for the contacts 34 and the slip ring '36 we have found that these contacts and slip ring are most preferably made from coin silver, and to provide proper electrical and mechanical properties they are preferably plated with a gold alloy, although rhodium or other suitable plating materials may be employed.

Commutator plate 30 is provided centrally with an aperture 50 in which is disposed a bearing 52 to support output shaft 26 which extends therethrough. Mounted on the end of shaft 26 is a disc-like rotor 54 on which is mounted the brush assembly 56. Brush assembly 56 includes brush means 58 which is adapted to sequentially engage the contacts 34 and a brush means 60 which is adapted to ride in surface-to-surface relation with the slip ring 36. With such an arrangement it will be seen that when motor 24 is energized to rotate shaft 26 the brush assembly 56 will move over the contacts 34 and the slip ring 36 to sequentially close electrical circuits between the contacts and the slip ring to supply information to suitable transmitting means (not shown). In this connection it will be understood that the terminals 40 and 44 of the contacts 34 and the slip ring 36, respectively, are adapted to have connected thereto suitable conducting means such as Wires (not shown) which wires can pass out of cylindrical member 12 through the openings 20 and 22.

In accordance with the present invention each of the contacts 34 is preferably an elongated rectangle having its major axis extending in a radial direction on said commutating plate 30. In lieu of the rectangular configuration of contacts 34, wedge shaped contacts may be employed. In this connection it will be understood that Wedge shaped contacts would have their edges extending along radii of commutator plate 30. The reason for the inclusion of rectangular or wedge shaped contacts will become clear as this description proceeds. Brush means 58 which engages in sequence the contacts 34 comprises a pair of plate-like brush holders 62 and 64 having offset arms 66 and 68, respectively, and, superposed main sup port portions 70 and 72, respectively. The support portions 70 and 72 are each provided with an elongated apertu-re T4 and 76, respectively, and a small circular aperture 78 and 80, respectively, for reasons which will appear hereinafter. Preferably the brush holders 62 and 64 are made of a suitable resilient electrically conducting material such as, for instance, beryllium copper, although Phosphor-bronze or other suitable material may be employed.

Secured to each of the olfset portions 66 and 68 of support means 62 and 64 are brush members 82 and 84, respectively. The brush members 82 and 84 may be made of any suitable material, but we prefer to use metallic materials such as a palladium, platinum, gold, silver, copper alloy of undisclosed proportions as sold under the trade designation Paliney #7 by John M. Ney Co., or an alloy of silver, cadmium, nickel and copper as sold by P. R. Malloy 00. under the trade name Elkonium. Of course, other suitable brush materials may be employed and in this connection silver graphite would be a satisfactory although not preferred material. The brush members 82 and 84 are connected to the oifset portions 66 and 68 in any suitable manner as by spot welding.

At the free end of each of the brush members 82 and 84 is a brush 86 and 88, respectively, which brushes are proportioned to have a longitudinal extent (length) of between 1.4 and 2.5 times the spacing between adjacent rectangular contacts. Most preferably the brushes 86 and 88 have a longitudinal extent of about 1.85 times the spacing between adjacent contacts. It will be seen that brushes 86 and 88 are displaced (offset) transversally of one another relative to their projected path of movement over the contacts 34. Moreover, it will be seen that the brushes as and 88 are offset relative to one another in the direction of their path of movement. This second offset, that is the offset in the longitudinal direction, is adjustable since the brush means 58 is secured to the rotor by means of a screw 90 which extends through the elongated apertures 74 and 76. When screw 90 is loosened the longitudinal displacement oi brushes 86 and 88 may be adjusted merely by sliding the brush support means 62 and 64 relative to one another as permitted by the elongated apertures 74 and 76. When they are properly adjusted for position, screw 90 is tightened which will cause the insulating wafers 92 and 94 rover-lying and underlying respectively the brush means 58 to clamp said brush means in fixed position.

The advantage of a brush assembly as described above may be best illustrated by describing a specific cornmutator plate with specific proportions. In a commutator plate now being produced the rectangular contacts have a radial extent of .125 inch and a length in the direction of the circular row of .028 inch. The spacing between adjacent contacts at the center line is about .0165 inch. Assuming a brush moving over said contacts is made in accordance with the preferred embodiment of this invention so that it has a longitudinal dimension of 1.85 times the con-tact spacing the longitudinal extent of the contact will be .031 inch. However, due to irregularities along the leading and trailing edges of the brushes the actual electrical engagement will be equivalent to a brush approximately 80% as long as the mechanical dimension given above or .025 inch. in a break-before-make system, that is in a system in which every other contact is energized and the remainder deenergized, with each contact the same size as described above, the on-time for a single brush of the dimensions stated above can be calculated as follows:

On time: 60%

Now, if two such brushes are olfset longitudinally but are not transversely oiTse-t and assuming for purposes of mechanical expediency that the trailing edge oi the forward brush cannot be closer than .010 inch to the leading edge of the rear-ward brush, then the on-time for such an arrangement would be calculated as follows:

.088 On time- .089

On time=99% From the foregoing calculations it will be seen that for any given contact arrangement and for a specified longitudinal dimension of any brush element engaging said contacts there is a gap in the achievable on-time between a value of around 60% and a value around 100%. While, as was stated hereinbetore, such intermediate on-times can be achieved by modifying the plate this would be undesirable due to the necessity of having a wide variety of different plates. As stated hereinbefore, the dimension of the brushes is fixed due to the fact that optimum commutation is achieved only with a brush having the desired relationship to the contact spacing.

However, by offsetting the brushes laterally any ontime between 60% and 100% can be achieved merely by adjusting the extent of longitudinal offset between the two associated brushes which adjustment is permitted only because the brushes have been laterally oifset.

With the provision of laterally oifset brushes a problem arises. If circular contacts are employed neither brush will be able to ride along the circle defining the centers oi the contacts. Accordingly, each brush will engage the leading contact edge of each circular contact at an angle which will tend to twist the brush. Over a substantial period of time this will have a deleterious eiiect. Furthermore, the gap between circular contacts over which each of the laterally spaced brushes pass may vary considerably which will affect the onatime that is so critical. To overcome this we prefer to employ contacts which have linear leading and trailing edges so as to eliminate the shortcomings described above. Moreover, with rectangular or wedge shaped contacts there is more space in the radial direction to accommodate the laterally ioifset brushes thereby facilitating manufacture.

Naturally, the brushes S6 and 88 are electrically connected. The electrical connection between them is atfected by means of the surface-to-surtace contact between the brush supports 70 and 72. Moreover, the brush means 58 is electrically connected to the brush means 60 which engages slip ring 36. This connection is effected .by connecting a wire to the brush assembly 58 through the registered apertures 78 and 80 and to any suitable portion of the brush holder for brush 60. As shown herein, brush 60 is mounted on rotor 54 by means of a screw 96 extending through insulating w'afers 98 and i100 and the brush holder 101 for brush 60.

The operation of the commutation switch is illustrated in FIGS. 4, 5 and 6. With the motor 24 rotating and with the brushes 86 and 88 engaging a contact 34a which contact will be assumed to be an energized (E) contact a circuit will be closed between the contact 34a and the slip ring 86. As rotor 54 continues to rotate under the driving of motor 24 the leading edge 86a oi brush 86 will pass over the trailing edge 34a of contact 34 and will tend to dip down into the space between the contact 34a and the contact 34b due to the self bias of brush member 82 whereby to cause a scraping of the bottom surface of brush 86 along the upper corner of the controlling edge of the contact 34a. At the same time brush 88 will remain in full engagement with the contact 34a and the circuit will remain established as heretofore described (FIG. 5). Thereafter, brush 86 will engage the leading edge 34b" of de-energized (D) contact 34b and will be wiped thereby and will then move into surface t-o-surface relation with that contact and brush 88 will become disengaged from the contact 34a in the same manner as brush 86 previously became disengaged, and will thereatter engage the leading edge 34b of contact 34b and scrape along said lead-ing edge as brush 86 previously did to complete the disengagement of the brush means 58 from the contact 34a to open the circuit between contact 34a and the slip ring (FIG. 6). This will be the elf-time period. The subsequent disengagement from contact 34b and engagement of contact 340 will establish a new circuit to commence a new duty cycle.

While we have herein shown and described the preferred form of the present invention and have suggested various changes and modifications therein, other changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of the invention.

What we claim is:

1. In -a commutation switch, a commutation plate having a circular row of equi-spaced substantially identical raised contacts and a slip ring concentric with said circular row of contacts, alternate contacts in said circular row being adapted to be connected to electrical devices and the remaining of said contacts being unconnected, and rotatable brush means engageable with said contacts and slip ring tor sequentially electrically connecting said contacts to said slip ring, said brush means including a brush engaging said slip ring and a pair of laterally and longitudinally ofiset brushes both engaging in sequence each of said contacts in said circular row of contacts, and resilient means biasing said pair of brushes into engagement with said circular row of contacts.

2. In a commutation switch, a commutation plate having a circular row of equi-spaced substantially identical raised contacts and a slip ring concentric with said circular row of contacts, alternate contacts in said circular row being adapted to be connected to electrical devices and the remaining contacts being adapted to be unconnected, alternate contacts in said circular row being adapted to be connected to electrical devices and the remaining of said contacts being unconnected, and rotatable brush means engageable with said contacts and slip ring for sequentially electrically connecting said contacts to said slip ring, said brush means including a brush engaging said slip ring and a pair of laterally and longitudinally ofiset brushes both engaging in sequence each of said contacts in said circular row of contacts,

resilient means biasing said pair of brushes into engage ment with said circular row of contacts, and means for permitting the adjustment of the extent of longitudinal offset between said offset brushes.

3. In a commutation switch, a commutation plate having a circular row of equi-spaced substantially identical raised contacts and a slip ring concentric with said circular row of contacts, alternate contacts in said circular row being adapted to be connected to electrical devices and the remaining of said contacts being unconneoted, and rotatable brush means engageable with said contacts and slip ring for sequentially electrically connecting said contacts to said slip ring, said brush means including a brush engaging said slip ring and a pair of laterally and longitudinally oliset brushes both engag- 6(2). ing in sequence each of said contacts in said circular row of contacts, and resilient means biasing said pair of brushes into engagement with said circular row of contacts, both of said offset brushes having a longitudinal dimension between about 1.4 and 2.5 times the space between adjacent contacts.

4. In a commutation switch, a commutation plate having a circular row of equi-spaced substantially identical raised contacts and a slip ring concentric with said circular row of contacts, alternate contacts in said circular row being adapted to be connected to electrical devices and the remaining of said contacts being unconnected, and rotatable brush means engageable with said contacts and slip ring for sequentially electrically connecting said contacts to said slip rings, said brush means including a brush engaging said slip ring and a pair of laterally and longitudinally offset brushes both engaging in sequence eachof said contacts in said circular row of cont-acts, and resilient means biasing said pair of brushes into engagement with said circular row of contacts, both of said offset brushes having a longitudinal dimension of about 1.85 times the space between adjacent contacts, and means for permitting the adjustment of the extent of longitudinal offset between said oliset brushes.

References Cited in the file of this patent UNITED STATES PATENTS 1,835,788 Knoop Dec. 8, 1931 2,402,736 Dav-is June 25, 1946 2,634,342 B-aechler Apr. 7, 1953 2,678,985 Smith May 18, 1954 2,848,567 Estoppey Aug. 19, 1958 2,866,861 Lynch Dec. 30, 1958 2,894,096 Schacht July 7, 1959 2,975,246 Lynch et al Mar. 14, 1961 

1. IN A COMMUTATION SWITCH, A COMMUTATION PLATE HAVING A CIRCULAR ROW OF EQUI-SPACED SUBSTANTIALLY IDENTICAL RAISED CONTACTS AND A SLIP RING CONCENTRIC WITH SAID CIRCULAR ROW OF CONTACTS, ALTERNATE CONTACTS IN SAID CIRCULAR ROW BEING ADAPTED TO BE CONNECTED TO ELECTRICAL DEVICES AND THE REMAINING OF SAID CONTACTS BEING UNCONNECTED, AND ROTATABLE BRUSH MEANS ENGAGEABLE WITH SAID CONTACTS AND SLIP RING FOR SEQUENTIALLY CONNECTING SAID CONTACTS TO SAID SLIP RING, SAID BRUSH MEANS INCLUDING A BRUSH ENGAGING SAID SLIP RING AND A PAIR OF LATERALLY AND LONGITUDINALLY OFFSET BRUSHES BOTH ENGAGING IN SEQUENCE EACH OF SAID CONTACTS OF SAID CIRCULAR ROW OF CONTACTS, AND RESILIENT MEANS BIASING SAID PAIR OF BRUSHES INTO ENGAGEMENT WITH SAID CIRCULAR ROW OF CONTACTS. 